1. Field of the Invention
The present invention generally relates to a solid state image pick-up device and apparatus and, more particularly, to a solid state image pick-up device having the two-dimensional filtering function and providing video signals filtered in real time.
2. Description of the Related Art
Recently, various techniques have been developed to electronically pick-up objects by using a solid state image pick-up device such as CCD and MOS image sensors, which are realized as video cameras and electronic still cameras.
This type of solid state image device (image sensor) basically comprises several photoelectric sections arranged as a matrix to sequentially read signal charges generated and stored in response to the quantity of incident light by each photoelectric section in time series through a signal-charge transfer unit (transfer register). The solid state image pick-up device such as a MOS image sensor has the function to hold the signal charges stored in photoelectric section and deletes the signal charges stored in the sections by receiving the reset signal which is separately given independently of reading of signal charges stored in the sections.
Therefore, when treating video signals obtained through the above image sensor, two-dimensional high-pass filtering to extract the edge component of images by obtaining the differential value between adjacent pixels and two-dimensional filtering to correct uneven illumination are frequently used as image signal processing. The two-dimensional filtering is basically made by executing convolute integration between a noticed pixel, several ambient pixels of it, and prescribed weighting factor. That is, the two-dimensional filtering is conventionally generally realized by storing the pixel signals read in time series from a solid state image pick-up device in shift registers for "n" lines, obtaining (n.times.m) pixel signals by applying retardation processing to the pixel signals obtained from each shift register, and multiplying each signal by the prescribed filter factor to obtain the total sum.
The CCD image sensor is configured so that each of said signal charges will be read in time series by vertically transferring the signal charges stored in several photoelectric sections for each column respectively and horizontally transferring the signal charges read in lines at the output end. The MOS image sensor is configured so that each of said signal charges will be read in time series by sequentially designating photoelectric sections in a matrix in the line and column directions.
However, to make the two-dimensional filtering circuit to apply two-dimensional filtering to the video signals (signal charges) read from the above sensors in time series as a dedicated hardware circuit and obtain the required filtering output by externally connecting the circuit to the output stage of a solid state image pick-up device, a large-scale image processor is necessary. Moreover, there is a disadvantage that filtering output cannot be obtained in real time.
Therefore, in the prior art, there are disadvantages that a dedicated two-dimensional filtering circuit should be made as an outside circuit of said solid state image pick-up device in order to apply two-dimensional filtering to the video signals obtained from the solid state image pick-up device, a large-scale image processor is necessary, and no filtering output can be obtained in real time.